To provide wireless connectivity between a portable processing device (e.g., laptop computer) and other computers (laptops, servers, etc.), peripherals (e.g., printers, mouse, keyboard, etc.) or communication devices (modem, smart phones, etc.) it is necessary to equip the portable device with an antenna. For example, with portable laptop computers, an antenna may be located either external to the device or integrated (embedded) within the device (e.g., embedded in the display unit).
For example, FIG. 1 is a diagram illustrating various embodiments for providing external antennas for a laptop computer. For instance, an antenna (100) can be located at the top of a display unit of the laptop. Alternatively, an antenna (101) can be located on a PC card (102). The laptop computer will provide optimum wireless connection performance when the antenna is mounted on the top of the display due to the very good RF (radio frequency) clearance. There are disadvantages, however, associated with laptop designs with external antennas including, for example, high manufacture costs, possible reduction of the strength of the antenna (e.g., for a PC card antenna (102)), susceptibility of damage, and the effects on the appearance of the laptop due to the antenna.
Other conventional laptop antenna designs include embedded designs wherein one or more antennas are integrally built (embedded antenna) within a laptop. For example, FIG. 2 illustrates conventional embedded antenna implementations, wherein one or more antennas (200, 201, 202) (e.g., whip-like or slot embedded antenna) are embedded in a laptop display. In one conventional embodiment, two antennas are typically used (although applications implementing one antenna are possible). In particular, two embedded antennas (200, 201) can be placed on the left and right edges of the display. The use of two antennas (as opposed to one antenna) will reduce the blockage caused by the display in some directions and provide space diversity to the wireless communication system.
In another conventional configuration, one antenna (200 or 201) is disposed on one side of the display and a second antenna (202) is disposed in an upper portion of the display. This antenna configuration may also provide antenna polarization diversity depending on the antenna design used.
Although embedded antenna designs can overcome some of the above-mentioned disadvantages associated with external antenna designs (e.g., less susceptible to damage), embedded antenna designs typically do not perform as well as external antennas. To improve the performance of an embedded antenna, the antenna is preferably disposed at a certain distance from any metal component of a laptop. For example, depending on the laptop design and the antenna type used, the distance between the antenna and any metal component should be at least 10 mm. Another disadvantage associated with embedded antenna designs is that the size of the laptop must be increased to accommodate antenna placement, especially when two or more antennas are used (as shown in FIG. 2).
U.S. Pat. No. 6,339,400, issued to Flint et al. on Jan. 15, 2002, entitled “Integrated Antenna For Laptop Applications”, which is commonly assigned and incorporated herein by reference, discloses various embedded antenna designs, which provide improvements over conventional embedded antenna designs. More specifically, the patent describes various embodiments wherein embedded antennas are (i) disposed on edges of the laptop display wherein a metal frame of the display unit is used as a ground plane for the antennas, and/or (ii) formed on a conductive RF shielding foil disposed on the back of the display, wherein coaxial transmission lines are used to feed the antennas (e.g., the center conductors are coupled to the radiating element of the antenna and the outer (ground connector) is coupled to the metal rim of the display unit). Advantageously, these integrated designs support many antenna types, such as slot antennas, inverted-F antenna and notch antennas, and provide many advantages such as smaller antenna size, low manufacturing costs, compatibility with standard industrial laptop/display architectures, and reliable performance.
Continuing advances in wireless communications technology has lead to significant interest in development and implementation of wireless computer applications. For instance, spontaneous (ad hoc) wireless network connectivity can be implemented using the currently emerging “Bluetooth” networking protocol. Briefly, Bluetooth is a protocol for providing short-range wireless radio links between Bluetooth-enabled devices (such as smartphones, cellular phone, pagers, PDAs, laptop computers, mobile units, etc.). Bluetooth enabled devices comprise a small, high performance, low-power, integrated radio transceiver chip comprising a baseband controller for processing input/output baseband signals using a frequency-hop spread-spectrum system, as well as a modulator/demodulator for modulating/demodulating a carrier frequency in the 2.4 GHz ISM (industrial-scientific-medical) band.
Currently, the 2.4 GHz ISM band is widely used in wireless network connectivity. By way of example, many laptop computers incorporate Bluetooth technology as a cable replacement between portable and/or fixed electronic devices and IEEE 802.11b technology for WLAN (wireless local area network). If an 802.11b device is used, the 2.4 GHz band can provide up to 11 Mbps data rate. For much higher data rates, the 5 GHz U-NII (unlicensed national information infrastructure) can be used. U-NII devices operating on the 5.15-5.35 GHz frequency range can provide data rates up to 54 Mbps.
As a result, the demand for a dual-band antenna operating at both bands is increasing. Dual-band antennas with one feed have some advantages over multi-feed antennas for wireless LAN applications. As wireless communications among processing devices become increasingly popular and increasingly complex, a need exists for a compact integrated dual-band antenna having reduced costs and reliable performance.